We have an acquaintance who "Facebooks" strangers--which is code for "takes sneaky cell phone pictures for the sole purpose of posting them and ridiculing the subjects." I have lost all respect for him. I think it's cowardly, pathetic, juvenile, passive-aggressive, and highlights his own low self-esteem, though, to the untrained eye, it masquerades as superiority. And many of his "followers" appear to have untrained eyes--they love it.
It will come as no surprise that I, too, consider it highly invasive to photograph people, for whatever reason, without their permission because the pictures can then be potentially put to a variety of unsavory uses.